Serology Investigationand Molecular Characterization Of Avian Hepatitis E Virus Infection In The Flocks, China

Avian hepatitis E virus (HEV), the causative agent of big liver and spleen (BLS) diseaseor hepatitis-splenomegaly (HS) syndrome, mainly infects30-72weeks old aged broilerbreeder hens and laying hens and causes increasing mortality, egg reduction (20-40%), redfluid in the abdomen, regressive ovaries and enlarged liver and spleen in chickens. Thediseases caused heavy economic losses in Australia poultry. There were also few case reportsin China.Avian HEV, which belonged to the Hepeviridae family, is non-enveloped, single-stranded, positive-sense RNA virus. The full length of avian HEV genome is6.6kb and is600bp shorter than the length of mammalian HEV complete genome. The complete genomeof avian HEV contains three open reading frames (ORF), ORF1,2and3, besides the5’ capand3’ PolyA structure. The ORF2gene encodes the capsid protein and contains primaryepitopes of avian HEV.An indirect ELISA was established for detection of anti-avian HEV antibody using thecoated antigen of avian HEV truncated ORF2protein which was based on CaHEV isolatethrough optimizing the different conditions. We investigated epidemiology of38chickenfarms in12provinces for avian HEV infection using the indirect ELISA. It was shown thatavian HEV antibodies were detected in all34flocks. But the positive rate for avian HEVantibody among34flocks was significantly different. The positive rate reached86.2%in oneShanghai flock. There were2528of positive serum for avian HEV antibody in5755serumcollected from the38flocks. It was suggested that avian HEV infection has been veryprevalent in China. Based on the datas, it was obvious that the positive rate of foreign breedswas significantly higher and30-39week-old chickens had higher positive rate.In addition, fecal and bile samples were collected from chickens with HS syndrome orBLS disease in some fields from6provinces. Partial ORF2gene of avian HEV was detectedusing RT-PCR method based on the primers described by other researchers. It was shown that11of90bile samples were positive and8of76fecal samples were positive. Meanwhile, sequences analysis revealed that the obtained sequences showed the highest identity withEuropean isolates and phylogenetic trees showed that the isolates in this study were closelyrelated to the Europe isolates and belonged to avian HEV genotype3.